(a) Field of the Invention
The present invention relates to a magnetic mono-component toner composition, and more particularly to a magnetic mono-component toner composition having such good flowability that it provides smooth toner supply even when the developing roller surface has been worn due to long time use, and having such excellent uniform chargeability that it prevents image deterioration (“wave” patterns of toner may form on developing roller, that is, magnetic sleeve) by forming an uniform toner layer on the developing roller.
(b) Description of the Related Art
Generally, the dry-type developing methods of the electrophotography can be classified into two-component developing method using a two-component developer comprising a magnetic carrier and a toner, and mono-component developing method using a mono-component developer comprising a toner only without a carrier. In general, the mono-component developing method can realize smaller developing unit, lower manufacturing cost and easy maintenance. Therefore, the number of copiers and printers using the mono-component developing method has been spreading recently, and also the printing speed is improving significantly.
Differing from the two-component developing method using a two-component developer comprising carrier particles that carry toner particle, the flowability of toner particle themselves greatly affects movement of toner in the magnetic mono-component toner.
The non-magnetic mono-component toner applies pressure on the developing roller using a blade made of metal or polymer to control the thickness of toner layer formed on the developing roller, and the two-component toner moves the toner particle by triboelectrification resulting from friction with the carrier particles. In magnetic mono-component developer, on the other hand, a toner regulating member (doctor blade) is arranged so as to make contact with a developing roller, and the mono-component toner is triboelectrically charged by passing between toner regulating member and developing roller, and the charged toner is maintained on the surface of the developing roller by electrostatic force.
Accordingly, enough flowability to easily transport to the toner regulating member is required for a magnetic mono-component toner. If the surface of the developing roller (sleeve) is worn by long time use, that is, if the sleeve surface becomes relatively smooth, the triboelectrification becomes non-uniform and the toner particle may agglomerate to form a wave pattern on the surface of the developing roller, and thereby cause image deterioration.
To solve this problem, a method of reducing folwability of the toner to increase pressure applied to the toner when it passes through the toner regulating member and to reduce formation of the wave pattern has been developed. However, this method inevitably worsens supply of toner and makes it impossible to obtain an uniform image density.
Accordingly, research on a magnetic mono-component toner having such good flowability that the toner is supplied without problems, and having such excellent uniform chargeability that an uniform toner layer is formed on the developing roller even after long time use, are highly required.